| 1. |
- Buchanan, Claire, et al.
(författare)
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Coordination crosslinking of helical substituted oligoamide nanorods with Cu(II)
- 2020
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Ingår i: Supramolecular Chemistry. - : Informa UK Limited. - 1061-0278 .- 1029-0478. ; 32:3, s. 222-232
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Tidskriftsartikel (refereegranskat)abstract
- Substituted oligoamides are short sequences of unnatural amino acids. Oligoamides made entirely of β3 amino acids yield helical monomers that, if N-acylated, assemble into nanorod structures via a supramolecular assembly motif. In this work, coordination crosslinking was used to create complex nanomaterials from oligoamides WKLWEL (KE) and WELWEL (EE) (the letters denote the analogous α-amino acids). Upon Cu(II) addition, atomic force microscopy and small angle neutron scattering revealed morphologic changes specific to KE but absent in EE. Vibration spectroscopy measurements revealed that Cu(II) can coordinate to the amine moieties of the side chains, without direct effect on the backbone amides. While coordination in excess solvent lead to regular nanostructures, fast drying of the sample yielded oligoamide templated crystallization of CuCl2. The metal coordination crosslinking of supramolecular assemblies as reported here is the first realization of a metallosupramolecular framework structure.
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| 2. |
- Cao, Cheng, et al.
(författare)
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Drug-Directed Morphology Changes in Polymerization-Induced Self-Assembly (PISA) Influence the Biological Behavior of Nanoparticles
- 2020
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 12:27, s. 30221-30233
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Tidskriftsartikel (refereegranskat)abstract
- The effect of the hydrophobic block length on the morphologies of polymerization-induced self-assembled (PISA) nanoparticles is well understood. However, the influence of drug loading on the phase morphology of the nanoparticles during the PISA process, and the resulting biological function of PISA nanoparticles, has barely been investigated. In this work, we show that the addition of a drug, curcumin, during the PISA process shifts the phase diagram toward different morphologies. The PISA system was based on hydrophilic poly(2-(methacryloyloxy)ethylphosphorylcholine) (PMPC), which was chain extended with hydrophobic methyl methacrylate (MMA) in various concentrations of curcumin. According to transmission electron microscopy, the presence of curcumin led to the transition of, for example, worms to polymersome and micelles to worms analysis. To understand the interaction between polymer particles and drug, small-angle X-ray scattering (SAXS), small-angle neutron scattering (SANS), and fluorescence lifetime measurements were carried out. These measurements show that curcumin is predominantly located in the core in the case of micelles and worms while it is found in the shell of polymersomes. The change in morphology influences the cellular uptake by MCF-7 cells and the movement of the particles in multicellular cancer spheroids (3D model). With the increasing amount of drug, the cellular uptake of micelles and worms was enhanced with the increasing grafting density of MPC chains, which contrasts the decreasing cellular uptake in the higher drug-loaded polymersomes due to the lower shell hydration.
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| 3. |
- Conn, Charlotte E, et al.
(författare)
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Membrane Protein Structures in Lipid Bilayers; Small-Angle Neutron Scattering With Contrast-Matched Bicontinuous Cubic Phases
- 2020
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Ingår i: Frontiers in chemistry. - : Frontiers Media S.A.. - 2296-2646. ; 8
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Tidskriftsartikel (refereegranskat)abstract
- . Deuterated vesicles can be used to obtain the radius of gyration of membrane proteins, but protein-protein interference effects within the vesicles severely limits this method such that the protein structure cannot be modeled. We show herein that different membrane protein conformations can be distinguished within the lipid bilayer of the bicontinuous cubic phase using contrast-matching. Time-resolved studies performed using SANS illustrate the complex phase behavior in lyotropic liquid crystalline systems and emphasize the importance of this development. We believe that studying membrane protein structures and phase behavior in contrast-matched lipid bilayers will advance both biological and pharmaceutical applications of membrane-associated proteins, biosensors and food science.
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| 4. |
- Garvey, Christopher J., et al.
(författare)
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Molecular-Scale Understanding of the Embrittlement in Polyethylene Ocean Debris
- 2020
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Ingår i: Environmental Science and Technology. - : American Chemical Society (ACS). - 0013-936X .- 1520-5851. ; 54:18, s. 11173-11181
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Tidskriftsartikel (refereegranskat)abstract
- The fate of plastic waste is a pressing issue since it forms a visible and long-lived reminder of the environmental impact of consumer habits. In this study, we examine the structural changes in the lamellar arrangements of semicrystalline polyethylene (PE) packaging waste with the aim of understanding the physical mechanisms of embrittlement in PE exposed to the marine environment. PE microplastics and macroplastics from identifiable PE packaging were collected in the Atlantic Ocean and compared to new PE boxes. Several experimental techniques interrogate the effects of environmental exposure on their bulk and surface properties. Size exclusion chromatography determines the molecular weight distribution of the PE polymer chains and differential scanning calorimetry gives the crystallinity. Small- and wide-angle X-ray scattering examines the packing of PE chains into semicrystalline lamellae. Longitudinal acoustic mode Raman spectroscopy provides a complementary measurement of the length of PE polymer chains extending through the crystalline lamellar domains. While there is a high degree of uncertainty in the time scale for the changes, the overall picture at the molecular scale is that although PE becomes more crystalline with environmental exposure, the lamellar order present in new packing boxes is disrupted by the weathering process. This process has important implications for embrittlement and subsequent degradation.
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| 5. |
- Jacobs, Susan S., et al.
(författare)
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Home oxygen therapy for adults with chronic lung disease an official american thoracic society clinical practice guideline
- 2020
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Ingår i: American Journal of Respiratory and Critical Care Medicine. - 1073-449X. ; 202:10, s. 121-141
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Tidskriftsartikel (refereegranskat)abstract
- Background: Evidence-based guidelines are needed for effective delivery of home oxygen therapy to appropriate patients with chronic obstructive pulmonary disease (COPD) and interstitial lung disease (ILD). Methods: The multidisciplinary panel created six research questions using a modified Delphi approach. A systematic review of the literature was completed, and the Grading of Recommendations Assessment, Development and Evaluation approach was used to formulate clinical recommendations. Recommendations: The panel found varying quality and availability of evidence and made the following judgments: 1) strong recommendations for long-term oxygen use in patients with COPD (moderate-quality evidence) or ILD (low-quality evidence) with severe chronic resting hypoxemia, 2) a conditional recommendation against long-term oxygen use in patients with COPD with moderate chronic resting hypoxemia, 3) conditional recommendations for ambulatory oxygen use in patients with COPD (moderate-quality evidence) or ILD (low-quality evidence) with severe exertional hypoxemia, 4) a conditional recommendation for ambulatory liquidoxygen use in patients who are mobile outside the home and require .3 L/min of continuous-flow oxygen during exertion (very-lowquality evidence), and 5) a recommendation that patients and their caregivers receive education on oxygen equipment and safety (bestpractice statement). Conclusions: These guidelines provide the basis for evidence-based use of home oxygen therapy in adults with COPD or ILD but also highlight the need for additional research to guide clinical practice.
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| 6. |
- Jarrett, K. J., et al.
(författare)
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The spatial modulation of microfibril angle in the woody tissue of maturing tree stems studied with synchrotron radiation
- 2020
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Ingår i: Australian Journal of Botany. - : CSIRO Publishing. - 0067-1924 .- 1444-9862. ; 68:4, s. 267-274
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Tidskriftsartikel (refereegranskat)abstract
- Spatial variations in the microfibril angle (MFA) of cellulose are mapped on individual radial sections of wood from the maturing stems of Australian tree species (Acacia floribunda, Acacia suaveolens, Acacia doratoxylon, Acacia havilandiorum, Brachychiton populneus and Bertya cunninghamii) from different rainfall and soil nutrient availabilities using synchrotron wide angle X-ray scattering. For the three species with the smallest radial variation there is a clear linear relationship between the MFA with Young's modulus and wood density with data published previously for these samples. The other three samples show a large radially symmetric variation in MFA across the radial section either having a continuous change from large MFA in the stem's centre to small value close to the bark or the reverse, small MFA at the centre to larger values close to the bark. For these samples, a strong linear correlation between the Young's modulus and density and the MFA is not apparent. We conclude that spatially localised measurements of MFA provide an important insight in the adaptation of wood tissue to environmental conditions.
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| 7. |
- McCoy, Thomas M, et al.
(författare)
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Spontaneous Self-Assembly of Thermoresponsive Vesicles Using a Zwitterionic and an Anionic Surfactant
- 2020
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 21:11, s. 4569-4576
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Tidskriftsartikel (refereegranskat)abstract
- Spontaneous formation of vesicles from the self-assembly of two specific surfactants, one zwitterionic (oleyl amidopropyl betaine, OAPB) and the other anionic (Aerosol-OT, AOT), is explored in water using small-angle scattering techniques. Two factors were found to be critical in the formation of vesicles: surfactant ratio, as AOT concentrations less than equimolar with OAPB result in cylindrical micelles or mixtures of micellar structures, and salt concentration, whereby increasing the amount of NaCl promotes vesicle formation by reducing headgroup repulsions. Small-angle neutron scattering measurements reveal that the vesicles are approximately 30-40 nm in diameter, depending on sample composition. Small-angle X-ray scattering measurements suggest preferential partitioning of OAPB molecules on the vesicle inner layer to support vesicular packing. Heating the vesicles to physiological temperature (37 °C) causes them to collapse into smaller ellipsoidal micelles (2-3 nm), with higher salt concentrations (≥10 mM) inhibiting this transition. These aggregates could serve as responsive carriers for loading or unloading of aqueous cargoes such as drugs and pharmaceuticals, with temperature changes serving as a simple release/uptake mechanism.
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| 8. |
- Shou, Keyun, et al.
(författare)
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Effect of red blood cell shape changes on haemoglobin interactions and dynamics : a neutron scattering study
- 2020
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Ingår i: Royal Society Open Science. - : ROYAL SOC. - 2054-5703. ; 7:10
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Tidskriftsartikel (refereegranskat)abstract
- By using a combination of experimental neutron scattering techniques, it is possible to obtain a statistical perspective on red blood cell (RBC) shape in suspensions, and the inter-relationship with protein interactions and dynamics inside the confinement of the cell membrane. In this study, we examined the ultrastructure of RBC and protein-protein interactions of haemoglobin (Hb) in them using ultra-small-angle neutron scattering and small-angle neutron scattering (SANS). In addition, we used the neutron backscattering method to access Hb motion on the ns time scale and angstrom length scale. Quasi-elastic neutron scattering (QENS) experiments were performed to measure diffusive motion of Hb in RBCs and in an RBC lysate. By using QENS, we probed both internal Hb dynamics and global protein diffusion, on the accessible time scale and length scale by QENS. Shape changes of RBCs and variation of intracellular Hb concentration were induced by addition of the Na+-selective ionophore monensin and the K+-selective one, valinomycin. The experimental SANS and QENS results are discussed within the framework of crowded protein solutions, where free motion of Hb is obstructed by mutual interactions.
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| 9. |
- Wang, Guang, et al.
(författare)
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Evolution of structural dimensions in mesoporous template precursor from hexagonal lyotropic liquid crystals
- 2020
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Ingår i: Journal of Physics. - : Institute of Physics (IOP). - 0953-8984 .- 1361-648X. ; 32:7
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Tidskriftsartikel (refereegranskat)abstract
- Producing nanopores from hexagonal lyotropic liquid crystals (LLCs) templates requires not only retaining phase morphology of the templates but also precisely controlling structural dimensions of unit cells. In this study, SAXS and H-2 NMR are used to investigate dimensional evolutions of ternary systems consisting of polymerizable species, (ethylene glycol) diacrylate (PEGDA) and/or 2-hydroxyethyl methacrylate (HEMA), in a LLCs template of hexagonally packed cylinders formed from dodecyl trimethylammonium bromide (DTAB) and water. With the addition of those polymerizable species, the system rearranges into a new hexagonal system with a smaller aggregation number, smaller pores and a thicker pore wall thickness. The hexagonal system will coexist with an aqueous-rich phase containing isotropically distributed DTAB if sufficient PEGDA is applied but the single hexagonal system could be restored by partially replacing the PEGDA with HEMA. The mobility of DTAB molecules within the aggregates varies depending on monomer compositions. The changes in structural dimensions of the unit cells and phase behaviors after adding polymerizable monomers allow dimensional control of mesochannels and potentially enable the control of selectivity and robustness of polymerized nanomaterials via molecular design.
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| 10. |
- Wojciechowski, Jonathan P., et al.
(författare)
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Non-reversible heat-induced gelation of a biocompatible Fmoc-hexapeptide in water
- 2020
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Ingår i: Nanoscale. - : Royal Society of Chemistry. - 2040-3364 .- 2040-3372. ; 12:15, s. 8262-8267
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Tidskriftsartikel (refereegranskat)abstract
- Hydrogel materials which respond to changes in temperature are widely applicable for injectable drug delivery or tissue engineering applications. Here, we report the unsual heat-induced gelation behaviour of a low molecular weight gelator based on an Fmoc-hexapeptide, Fmoc-GFFRGD. We show that Fmoc-GFFRGD forms kinetically stable fibres when mixed with divalent cations (e.g. Ca2+). Gelation of the mixture occurs upon heating of the mixture which enables electrostatic screening by the divalent cations and hydrophobic collapse of the fibres to give a self-supporting hydrogel network that shows good biocompatibility with L929 fibroblast cells. This work highlights a unique mechanism to initiate heat-induced gelation which should find opportunities as a gelation trigger for injectable hydrogels or fundamental self-assembly applications.
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